Self-extracting mandrel for pumpedin-place-pile



K. w. PHILO 3,344,611 SELF-EXTRACTING MANDREL FOR PUMPED-IN-PLACE-PILE Oct. 3, 1967 Filed Nov. 9, 1964 KENNETH w. PHILO- //VVE/VTOR.

Yaw/wen /awnsen/ United States Patent 3,344,611 SELF-EXTRACTIN G MANDREL FOR PUMPED- IN-PLACE-PILE Kenneth W. Philo, 21 St. Francis Laue,

San Rafael, Calif. 94901 Filed Nov. 9, 1964, Ser. No. 409,362 6 Claims. (Cl. 61-53.64)

ABSTRACT OF THE DISCLOSURE A self-extracting mandrel, for insertion in the earth to form concrete pilings, having an outer segmented casing and a common connecting member disposed within the casing. The segments are individually attached to the connecting member to enable each of the segments to be progressively and selectively displaced relative to the other segments as fluid concrete is introduced into the mandrel casing.

This invention relates to a mandrel for forming structure-supporting concrete piles in the earth.

The desirability of forming concrete piles in place as contrasted with driving a previously formed concrete pile into the earth has been recognized in the prior art. Typical prior art apparatus for forming such piles usually includes a shell of thin steel mount-able upon a rugged mandrel or core of suflicient strength to be driven into the earths surface. After such prior art apparatus is in place, the mandrel is removed, leaving the thin steel shell in place, which shell is then filled with concrete. The steel shell must necessarily remain in the earth as part of the pile, but contribute little, if any, strength thereto. Obviously such shells increase the cost of the pile.

Prior art efforts to eliminate the expenses of such steel shells necessitate the use of powerful hoisting machinery to overcome skin friction between the shell and the earth which resists removal of the shell. Such hoisting machinery is both expensive and so cumbersome that its use in remote and/ or rugged terrain is uneconomical.

Therefore, it is an object of the present invention to provide a pile mandrel for use in forming concrete piles in place, which mandrel eliminates both the necessity for an expensive steel shell that is left in the ground and powerful hoisting machinery heretofore necessary for shell removal. This object is attained by providing a mandrel casing that is formed of two or more longitudinally extending segments. The segments are longitudinally slidable with respect to one another and are therefore capable of independent movement. Thus the skin friction at one segment which is momentarily sta-' tionary substantially equalizes the skin friction of another segment as the last named segment is moved upwardly during extraction of the mandrel casing. Relatively lightweight driving mechanism that is included in the structure is suflicient for driving the segments longitudinally with respect to one another, thus eliminating the necessity for powerful hoisting machinery present in certain prior art systems.

Another object is to provide a mandrel wherein the fluid concrete is compacted and compressed as the mandrel is withdrawn from the earth surface. Achievement of this object is made possible by a bearing plate disposed within the mandrel casing, which bearing plate is driven longitudinally with respect to the casing segments. Part or all of the reaction force present as the casing is being withdrawn is applied to the bearing plate, and the fluid concrete thereunder is thus compacted or compressed.

A feature and advantage of the present invention is that the degree of compaction or compression applied 3,344,611 Patented Oct. 3, 1967 to the fluid concrete is variable by varying the number of mandrel casing segments that are urged upwardly at a given time. Consequently, variations in the density and hardness of soils can be accommodated.

The exemplary embodiment of the present invention that is described in specific detail hereinafter includes a mandrel casing formed of four substantially identical segments conjoined to define a casing of generally square cross section. Each of the segments is longitudinally slid able with respect to the others. A hydraulic actuator is associated with each such segment, each of the actuators being commonly coupled to an internal sleeve so that one or more of the segments can be driven longitudinally with respect to the sleeve. The sleeve extends to the lower end of the casing, at which location a bearing plate is rigidly aflixed to the sleeve. Extending through the easing and the sleeve is a concrete conveying tube which tube terminates in an aperture in the bearing plate. An end cap for the lower end of the casing is provided to enclose the casing during driving of the mandrel into the earth surface. Only the end cap, a relatively inexpensive article, remains in the ground with the formed pile.

These, together with other objects, features and advantages Will be more apparent after referring to the following specification and accompanying drawings in which:

FIG. 1 is an elevation view of the mandrel in place in the ground before commencement of concrete pumping, portions being broken away or section to reveal internal details;

FIG. 2 is similar to FIG. 1, showing the apparatus as concrete is being pumped in;

FIG. 3 is sirrrilar to FIG. 1, showing the apparatus at an early stage of the removal procedure;

FIG. 4 is similar to FIG. 3, showing the apparatus at a subsequent stage of removal;

FIG. 5 is a cross-sectional view taken along line 55 of FIG. 1;

FIG. 6 is a cross-sectional view taken along line 66 of FIG. 4; and

FIG. 7 is a cross-sectional view taken along line 77 of FIG. 1.

Referring more particuarly to the drawings, reference numeral 12 indicates a casing formed, in the exemplary embodiment herein shown in detail, by four segments 12a, 12b, 12c and 12d. The segments are conjoined along longitudinally extending seams 14 which seams afford longitudinal movement between adjacent segments. A seam of the type shown in FIG. 6, wherein each segment is provided with a longitudinally extending groove 16 and a tongue 18 receivable in the groove, has been found satisfactory. Segments 12a-12d are formed of steel or like material having sufiicient strength to withstand forces necessary for driving the mandrel into the earth surface.

An end cap 20 includes a rim 22 for receiving the lower end of casing 12 therein and is formed of steel or like earth impervious material of sufficient strength to withstand the stresses present during placement of the pile into the earth surface.

Adjacent the lower end of the casing and within the casing is a bearing plate 24 having an outer periphery cylinder has a piston rod reciprocably driven with respect thereto, cylinder 28a having a piston rod 30a secured to casing segment 12a, cylinder 28b having a piston rod 30b secured to casing segment 12b, etc. Each of the cylinders is double acting, by which is meant that rod 30 can be either driven into or out of the respective cylinder. For this purpose each cylinder is provided with a pair of hydraulic lines 36 which extend exterior of the casing.

Bearing plate 24 is centrally apertured as at 34 for communicating the interior of a concrete conveying tube 38 below the bearing plate. Concrete conveying tube 38 extends interiorly of casing 12 up to the top end thereof. A quarter bend 40 is provided for directing the tube through one of the segment walls, such as 12d, which wall is formed with an elongate slot 42 of length substantially equal to the throw of hydraulic cylinders 28. Tube 38 extends exteriorly of the mandrel casing, as at 44, to afford connection of conventional concrete pumping apparatus, not shown, to the concrete tube.

The operation of the aforedescribed embodiment of the present invention will be understood by assuming that the structure has been driven into earth surface E to a suitable depth by conventional pile driving equipment. FIG. 1 depicts the relative disposition of the portions of the structure during such pile driving operation and prior to commencement of concrete pumping. It is preferred that cylinders 28 be so energized during driving of the mandrel as to retain bearing plate 24 in contact with end cap 20 to enhance the rigidity of the mandrel.

When the mandrel is in place, a source of fluid concrete, not shown, is attached to tube 38 at exterior end 44, and concrete aggregate is pumped through tube 38 simultaneously with actuation of all cylinders 28 to raise bearing plate 24 with respect to end cap 20 as the aggregate is pumped in. See FIG. 2.

The upward movement of bearing plate 24 terminates when the plate is moved the distance equal to the stroke of hydraulic cylinders 28. Opposing hydraulic cylinders 28b and 28d are now actuated while the other pair (28a and 28c) is maintained in the withdrawn position. As a result of such operation, segments 12b and 12d are moved upwardly, see FIG. 3, against two reaction forces, namely: the skin friction between the earth and stationary segments 12a and 120 and the force of the concrete aggregate against bearing plate 24. The latter phenomenon is desirable in that the concrete is compacted so that it flows into any voids or interstices in the soil. Upward movement of segments 12b and 12d is continued until cylinders 28!) and 28d have completed their strokes, at which time the last named cylinders are retained in the extended position and cylinders 28a and 280 are operated to raise segments 12a and 120 with respect to segments 12b and 12d and with respect to bearing plate 24. Such action is continued until the apparatus assumes the position shown in FIG. 4, the reactive forces for the upward movement of segments 12a and 12c being provided by the skin friction between the surrounding soil and segments 12b and 12d and the pressure of bearing plate 24 on the concrete therebelow.

Additional concrete is pumped into tube 38 and during such action bearing plate 24 is raised by simultaneous actuation of all hydraulic cylinders. Thereafter the remaining steps are repeated until the mandrel is free of the ground surface.

An ancillary feature of my improved mandre is shown in some detail in FIGS. 4 and 6. Each segment 12a-12d has a transverse joint 46 dividing each segment into upper and lower portions, which portions are joined by a splice plate 48. The splice plate and segment portions are suitably apertured to receive bolts or the like 50, which bolts pass through both the splice plate and the segment to secure the joint. By use of such ancillary feature, it is possible to provide a plurality of segmented mandrel lower portions and one upper portion wherein hydraulic cylinders 28 reside. Each of the lower portions can be driven in the ground, and the single upper hydraulic cylinder containing portion can be moved from site to site for placement of the concrete and extraction of the lower mandrel segment. This feature has obvious economic advantages.

An alternate mode of operation of the present apparatus, which is particularly desirable when formation of a large diameter pile is necessary, is the simultaneous operation of all cylinders as a consequence of which the total reactive force necessary to raise all segments against forces of gravity and skin friction is provided by the concrete aggregate beneath bearing plate 24. The force imposed by the bearing plate on the concrete aggregate compacts the aggregate and the surrounding soil so that the diameter of the pile is increased.

Still another alternate mode of operation is to withdraw the mandrel by moving only one segment upwardly in which case more reactive force is provided by the three stationary segments and less force is imposed on the aggregate below bearing plate 24.

Although a mandrel form having four segments arranged in a generally square configuration has been shown in detail hereinabove for the purposes of illustrating the features of my invention, it is to be understood that such specific embodiment is only exemplary and that the mandrel form can be provided wtih a circular, triangular, or polygonal configuration and that the casing can include any suitable number of segments. Additionally, bearing plate 24 can be provided with a plurality of apertures for receiving steel reinforcing rods therethrough should a reinforced pile be desired.

Although one embodiment of the present invention has been shown and described, it will be apparent that other adaptations and modifications can be made without departing from the true spirit and scope of the invention.

What is claimed is:

1. A self-extracting mandrel for forming in-place concrete piles comprising a plurality of segments forming an elongate tubular casing, said segments being mutually conjoined along slidable seams extending parallel to the longitudinal axis of said casing so that said segments are slidably movable with respect to one another, a conduit for conveying fluid concrete from about the upper end of said casing to the lower end thereof, a bearing plate slidably disposed in said casing and having a peripheral shape subshape of said casing so as to prevent passage of conrcete between the periphery of said plate and said casing, said plate defining an aperture for communicating said conduit through said plate, and means attached to said plate and each said segment for selectively and individually urging said casing segments longitudinally with respect to said plate.

2. A self-extracting mandrel for forming in-place concrete piles comprising a plurality of segments forming an elongate casing, said segments being mutually conjoined along seams substantially parallel to the longitudinal axis of the casing and being adapted for relative sliding movement along such seams, a bearing plate slidably disposed in said casing and having a peripheral shape substantially coextensive with the interior cross sectional shape of said casing so as to prevent passage of concrete between the periphery of said plate and said casing, and means attached to said plate and each said segment for selectively and individually urging said segments longitudinally with respect to all other segments and to said bearing plate.

3. A self-extracting mandrel for forming in-place concrete piles comprising a plurality of segments forming an elongate casing, said segments being mutually conjoinable along lines substantially parallel to the longitudinal axis of the casing and being adapted for relative sliding movement along such lines, a hollow shell member disposed within said casing, a conduit for conveying fluid concrete from the exterior of said casing and terminating adjacent the lower end of said shell, means for drivably connecting said shell to each said segment for relative movement of each said segment with respect to all other segments and to said shell member, and means for controlling said connecting means to selectively move said segments with respect to said shell and to all other segments.

4. A self-extracting mandrel for forming in-place concrete piles comprising casing means for forming a hollow elongate casing drivable into the earths surface, said casing means being defined by at least two segments, said segments being conjoined along slidable seams extending parallel to the longitudinal axis of said casing so that said segments are slidably movable with respect to one another, a concrete impervious tube extending from about the upper end of said casing to the lower end thereof for conveying fluid concrete to the lower end, a concrete impervious plate shaped substantially coextensively with the interior cross-section of said casing for bearing on concrete conveyed to the lower end of said casing, said plate defining an aperture for communicating said tube through said plate, and means attached to said plate and each said segment for selectively and individually urging said casing segments longitudinally with respect to said plate, whereby when the mandrel is in place in the earth and concrete is pumped through said tube below said plate, said segment urging means can be selectively actuated to raise respective segments and remove said casing while pumping concrete thereinto.

5. A mandrel for forming concrete piles in place comprising a plurality of elongate segments conjoined along parallel longitudinally extending seams to define an elongate hollow casing, said seams being formed to afiord relative longitudinal movement between said segments, an end cap for closing one end of said casing so that the casing can be driven into an earth surface, a tube extending longitudinally within said casing for conveying concrete from the end remote from said end cap to the end adjacent said end cap, a concrete impervious bearing plate having a peripheral shape substantially coextensive with the interior cross-section of said casing and being slidable therein between a first position proximate said end cap and a second position longitudinally spaced from said first position toward the opposite end of said casing, said bearing plate being apertured to communicate said concrete conveying tube therethrough, and means interior said casing attached to said bearing plate and to each said segment for individually and selectively driving each said segment longitudinally with respect to said bearing plate, whereby in extracting said mandrel during formation of a pile said segments are moved longitudinally with respect to each other and to said bearing plate.

6. A mandrel for forming concrete piles in place comprising four substantially identical segments conjoined along longitudinally extending parallel seams to define a hollow elongate casing of generally square cross section having an upper end and a lower end, said seams being adapted to afiord relative longitudinal movement between said segments, an end cap for closing the lower end of said casing, a shell disposed in said casing for sliding reciprocal movement with respect to said casing, a concrete impervious bearing plate aflixed to said shell adjacent the lower end of said casing, said bearing plate having an outer periphery substantially coextensive with the interior cross section of said casing so as to prevent passage of concrete between said plate and said casing, said bearing plate defining a concrete discharge aperture therethrough, a tube secured to said bearing plate in communication with said discharge aperture and extending toward the upper end of said casing for conveying concrete below said bearing plate and within said casing, four hydraulic actuators each having a cylinder and rod reciprocally movable with respect to said cylinder, each said actuator being mounted between one of said segments and said shell for individually and selectively moving each said segment in reciprocal movement with respect to said shell, and means exterior said casing for controlling said actuators.

References Cited UNITED STATES PATENTS 1,860,558 5/1932 Tada 61-53.64

FOREIGN PATENTS 644,258 1950 Great Britain. 280,095 1952 Switzerland.

DAVID J. WILLIAMOWSKY, Primary Examiner. JACOB SHAPIRO, Examiner. 

6. A MANDREL FOR FORMING CONCRETE PILES IN PLACE COMPRISING FOR SUBSTANTIALLY IDENTICAL SEGMENTS CONJOINED ALONG LONGITUDINALLY EXTENDING PARALLEL SEAMS TO DEFINE A HOLLOW ELONGATE CASING OF GENERALLY SQUARE CROSS SECTION HAVING AN UPPER END AND A LOWER END, SAID SEAMS BEING ADAPTED TO AFFORD RELATIVE LONGITUDINAL MOVEMENT BETWEEN SAID SEGMENTS, AN END CAP FOR CLOSING THE LOWER END OF SAID CASING, A SHELL DISPOSED IN SAID CASING FOR SLIDING RECIPROCAL MOVEMENT WITH RESPECT TO SAID CASING, A CONCRETE IMPERVIOUS BEARING PLATE AFFIXED TO SAID SHELL ADJACENT THE LOWER END OF SAID CASING, SAID BEARING PLATE HAVING AN OUTER PERIPHERY SUBSTANTIALLY COEXTENSIVE WITH THE INTERIOR CROSS SECTION OF SAID CASING SO AS TO PREVENT PASSAGE OF CONCRETE BETWEEN SAID PLATE AND SAID CASING, SAID BEARING PLATE DEFINING A CONCRETE DISCHARGE APERTURE THERETHROUGH, A TUBE SECURED TO SAID BEARING PLATE IN COMMUNICATION WITH SAID DISCHARGE APERTURE AND EXTENDING TOWARD TE UPPER END OF SAID CASING FOR CONVEYING CONCRETE BELOW SAID BEARING PLATE AND WITHIN SAID CASING, FOUR HYDRAULIC ACTUATORS EACH HAVING A CYLINDER AND ROD RECIPROCALLY MOVABLE WITH RESPECT TO SAID CYLINDER, EACH SAID ACTUATOR BEING MOUNTED BETWEEN ONE OF SAID SEGMENTS AND SAID SHELL FOR INDIVIDUALLY AND SELECTIVELY MOVING EACH SAID SEGMENT IN RECIPROCAL MOVEMENT WITH RESPECT TO SAID SHELL, AND MEANS EXTERIOR SAID CASING FOR CONTROLLING SAID ACTUATORS. 